Peel the cooked potatoes and cut into slices. Clean and rinse the spinach. Cook for five minutes in a saucepan with boiling hot salted water and drain in a sieve (or defrost frozen spinach leaves). Chop anchovy fillets, mix into spinach with freshly grated nutmeg and grated cheese.
Grease a gratin dish with butter, pour in spinach. “Prick” the potato slices into it like a roof tile. Season with salt and pour the whipped cream over them.
Put the dish in the preheated oven on the middle shelf and bake at 200 °C for 20 minutes.
Take out and serve on the spot.
Tip: Did you know that one bowl of spinach provides almost all the manganese and fiber you need?